Analysis of a Call Admission Control Algorithm for Real-Time Traffic in OFDMA Based Cellular Networks

In Orthogonal Frequency Division Multiple Access (OFDMA) networks there is variation of Grade of Service (GoS) experienced by the users within a cell. Hence a comprehensive performance analysis for such networks must include fairness of GoS considerations. Methods to enhance fairness of GoS include call admission control (CAC) schemes. A simple dynamic CAC scheme that responds to the bandwidth occupancy level is considered here. It leverages the fact that several regions within the cell offer a GoS that is much higher than acceptable. Users from such regions may be blocked even when sufficient resources are available, a technique which we refer to as forced blocking. Such forced blocking of GoS rich users, if performed at times of high bandwidth occupancy, may enable to improve the GoS of the remaining users. However, the rate of application of forced blocking to any class of users must be chosen such that the GoS of that class does not degrade beyond an acceptable limit. The performance of such an algorithm is studied in terms of parameters such as satisfied service area of the cell, min-max metric of fairness, variance of GoS and cell-average as well as cell-edge GoS. Both discrete event simulations (DES) and analytical models are employed in this performance study, for which First Come First Served (FCFS) performance serves as the reference.